Printer with helically arranged type divided into axially offset group

ABSTRACT

An electronic printer employs a character drum on which the elements are arranged along helical paths, and are divided into a plurality of discrete, axially offset character groups. An impact member is aligned with each of the character groups, and enables printing during concurrent rotation of the drum and axial movement of both the drum and the hammers synchronously past the object to be printed.

United States Patent 11 1 Kaczeus 1541 PRINTER WITH HELICALLY ARRANGEDTYPE nrvnmn INTO AXIALLY OFFSET GROUP Inventor: Steven L. Kaczeus,Chelmsford,

Mass.

Assignee: Printer Technology, 1110., Woburn,

Mass.

Filed: 'Jan. 15, 1971 Appl. No.: 106,850

US. Cl ..197/49, 101/93 c, 197/18 Int. Cl ..B4lj 1/22, B41j 1/32 Fieldof Search ..l0l/93; 197/55, 49,18

[56] References Cited UNITED STATES PATENTS 7/1958 Masterson ..l01/93 C[111 3,724,631 [451 Apr. 3, 1973 2,926,602 3/1960 MacDonald et al...101/93 C 3,331,316 7/1967 Bretti 197/] R 3,385,213 5/1968 Stephan..101/110 3,406,625 10/1968 Chamness et 31.... .197/55 X 3,442,3645/1969 Ragen ..197/49 3,599,772 8/1971 Comstock ..197/49 PrimaryExaminer-Edgar S. Burr Attorney-Peter L. Costas [5 7 ABSTRACT Anelectronic printer employs a character drum on which the elements arearranged along helical paths, and are divided into a plurality ofdiscrete, axially offset character groups. An impact member is alignedwith each of the character groups, and enables print-. ing duringconcurrent rotation of the drum and axial movement of both the drum andthe hammers synchronously past the object to be printed.

11 Claims, 7 Drawing Figures .1055 2 1/ POSITION/N6 un/vs l l iPATENTEHAPR 3 I975 SHEET 2 UF 2 FlG.6

COMP 2 CPU BUS 1 w u hm K "L Mn Im f 5 7 G F COMP? 1 CTR PRINTER WITHIIELICALLY ARRANGED TYPE DIVIDEDINTO AXIALLY OFFSET GROUP BACKGROUND OFTHE INVENTION In many instances, the maximum value is not realized incurrently available computer, mini-computer, teleindicated by theindicating means, and the actuating ployed therein. Although high speedprinters are available, their cost is often prohibitive or at leastdifficult to. justify, particularly in situations in which the outputcapacity that they provide greatly exceeds the overall capacity of thesystem. Moreover, such printers tend to be inappropriate for use inapplications in which human memory and reading capacities are involved.On the other hand, in contemporary mini-computer systems the presentlyavailable low speed printers often constitute the most limiting factor,and tend to militate against efficient operation.

Accordingly, it is the primary object of the present invention toprovide a medium speed electronic printer that is relatively inexpensiveto produce.

A more specific object is to provide such a printer that is capable ofprinting at least 30 characters per second, preferably about 60 90 andmost desirably about 80 120 characters per second.

It is also an object of the invention to provide a printer that isespecially suited for'use in mini-computer systems, both in terms ofoutput capacity and also in terms of cost. I

Another object is to provide a full character impact printer having, inaddition to the foregoing advantages, the capability of producing adesirable final copy format.

It has now been found that the foregoing and related objects can bereadily attained in an electronic character printer comprising a framehaving means thereon for positioning an object to be printed along alinear printing path, and a character drum mounted on the frame forconcurrent movement along the linear path and rotation about an axisparallel thereto. The drum has a multiplicity of character elementsarranged .about the circumference thereof and along helical paths, whichelements are divided into a plurality of discrete, axially ofr'setcharacter sets each comprised of a plurality of discrete axially off-setcharacter groups each provided by a multiplicity of character elements.Theprinter also includes a plurality of impact members mounted on theframe for synchronous movement along the linear path with the characterdrum. Each of the impact members cooperates with one of the charactergroups and is of a width substantially equal to the axial lengthencompassed by one of the character groups, and is aligned therewith topermit contact to be effected between any character element thereof andthe object, for printing during such concurrent movement and rotation.The printer has means for continuously rotating the character drum andfor moving the character drum and impact members along the linear path;means is also provided for dynamically indicating the angularrelationship between the character elements of each of the groups andthe impact member associated therewith. Means responsive to anelectronic input signal representative of matter to be printed is alsoprovided for actuating the impact members when a desired character forprinting is aligned therewith, as

means actuates the impact members independently of one another and suchthat the impact members cooperating with those groups of characterswhich are axially aligned along the circumference of the drum areactuated prior to actuation of the impact members cooperating with thecharacter ferentially therefrom.

lnaccordance with one embodiment, the charactergroups are substantiallyidentical and each of them constitutes a character set. The angle of thehelical paths, the character group off-set distance, and the rates ofrotation and linear movement are interrelated in such a manner that thecharacter elements of each of the groups sweep past only lln of thenumber of columns to be printed on the object, where n represents thenumber of character groups. In addition, each of the character setsextends incompletely about the drum circumference to providecircumferential spacing between the first and last character elementsthereof.

Alternatively, a pair of character groups may provide a single characterset, as a result of which the set will have two impact membersassociated with it. Preferably, the drum has a plurality of charactersets thereon with the character groups arranged sequen tially about thecircumference thereof. In such a case, the angle of the helical paths,the character group offset distance, and the rates of rotation andlinear movement are so interrelatedas to cause the character elements ofeach of the sets to sweep past only 1/1: of the total-number of columnsto be printed on the object, 11 representing the number of charactersets on the drum. Most desirably, three character sets andsix of impactmembers are provided. The drum is advantageously substantially free ofaxial and circumferential spacing between the last character element ofone of the groups and the first character element of another of thegroups to which it is adjacent. Generally, a character set will contain64 alphanumeric characters, and the printer will additionally includemeans furnishing ink to the object at the locations of contact withcharacter elements.

In accordance with the method! of the invention, an object to be printedis positioned along a linear printing path, and a character drum isconcurrently moved along the linear path and continuously rotated aboutan axis parallel thereto. The drum is provided with a multiplicity ofcharacter elements arranged about its circumference and along helicalpaths, and the elements are divided into a plurality of discrete,axially offset character groups. A plurality of impact members are movedsynchronously'with the drum along the linear path and with the objecttherebetween. Each of the impact members is of a width substantiallyequal to the axial length encompassed by one of the character groups,and is aligned therewith to permit contact to be effected between anycharacter element thereof and the object. The relationship between thecharacter elements of each of the groups and the impact memberassociated therewith is dynamically detected, and an electronic signalrepresentative thereof is generated. An electronic input signalrepresentative of the matter to be printed is also generated, and thedetecting signal and input signal are compared. The impact members areindependently and non-sequentially activated in response to the signalcomparison during such concurgroups spacedcircumrent movement androtation, thereby effecting contact of the object and the characterelements to reproduce the matter thereon. Preferably, contact of 60 90character elements per second is effected with the object, and mostdesirably the rate of contact is 80 120 character elements per second.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a printerembodying the present invention;

FIG. 2 is a side elevational view of a character drum, printing hammersand inking roll which may be utilized in the type of printer illustratedin FIG. 1, and drawn to a scale that is slightly enlarged therefrom;

FIG. 3 is a front elevational view of the character drum of FIG. 1,drawn to a slightly enlarged scale to more clearly illustrate thecharacter element arrangement thereon;

FIG. 4 is a fragmentary sectional view to an enlarged scale of anengagement mechanism for the printer carriage'assembly;

FIG. 5 is a schematic view of the developed surface of a second drumproviding a single character set, and of a pair of cooperating printinghammers employed therewith, drawn to an enlarged scale;

' FIG. 6 is a schematic view of another developed drum surface and ofprinting hammers used therewith, the drum providing three discretecharacter sets that are axially offset from one another and havecircumferential spacing between the first and the last elements thereof;and

FIG. 7 is a schematic view of an electronic logic design appropriate foruse in the printer of FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Turning now indetail to FIG. 1 of the appended drawings, therein illustrated is aprinter mechanism embodying the present invention and having a chassisproviding side elements 10 between which are journalled a hexagonalshaft 12 and a worm shaft 14, parallel thereto. The hexagonal shaft 12has a pulley 16 secured near one end and a timing wheel 18 at theopposite end thereof, and a character drum 20,having a hexagonal axialpassageway 22 therethrough, is slidably mounted on the shaft 12 betweenthe side elements 10 of the chassis. The drum 20 has a multiplicity ofcharacter elements 24 arranged along helical paths in six discreteaxially offset groups A B A,, 8,, A and 8,, as is best seen in FIG. 3and will be more fully described hereinafter.

' A hammer carriage assembly, generally designated by the numeral 25, ismounted upon the worm shaft 14 and includes a housing 26 supporting amultiplicity of hammers 28 therein. As is seen in FIG. 4, whichillustrates a mechanism by which the carriage assembly 25 may engage theworm shaft 14, the housing 26 has a transverse bore 27 for the wormshaft 14, and an intersecting perpendicular bore 29 in which is seated aslidable pin 31. The upper surface of the pin 31 has a transverse notch33 formed therein, and a short stud 35 projects downwardly from the pin31 through an opening 37 in the housing 26. Pivotably mounted above thepin 31 on an axle 39 is a pawl 41 having a nose portion 43 that is urgedby sprint 45 into engagement in the notch 33 of the pin 31, thusmaintaining the pin 31 in retracted position against the force of coilspring 47 positioned therebehind. As will be apparent, pivoting the pawl41 in a counter clockwise direction will disengage the nose portion 43and permit spring 47 to thrust pin 31 into driving engagement in thegroove 30 of the worm shaft 14. Disengagement of the pin 31 from shaft14 is effected by pivoting the resetting arm 49 on the shaft 51 againstthe force of spring 53. This causes the arm 49 to bear against the stud35 and return the pin 31 to a position for reengagement of the noseportion 43 in the notch 33.

A yoke 32 embraces the drum 20, and is secured to the carriage housing26 by a flexible drive cable 34. The cable 34 is supported upon thechassis by four pulleys 36 which in turn are rotatably mounted uponcorner posts 38. A coil spring 40 biases the carriage assembly 25 towardthe left end of the chassis as depicted in FIG. 1, and a dashpot orshock absorber 42 is affixed upon the side element 10 adjacent to thatend to prevent damaging impact upon return of the carriage assembly 25under the force of the spring 40. The

printer also includes an electric motor 44 from the shaft 59 of whichpower is transmitted through a belt 46 to the hexagonal shaft 12 and theworm shaft 14 through the pulleys 16, 48 on the ends thereof,respectively.

Energization of the motor 44 causes the worm shaft 14 and the hexagonalshaft 12 (and consequently the drum 20) to rotate continuously. Tocommence printing, engagement between the carriage assembly 25 and therotating worm shaft 14 is effected by release of the pin 31, in themanner described, which follows the groove 30 and thus causes axialmovement of .the assembly 25 from left to right in FIG. 1. Through thecable 34 and yoke 32, the drum 20 moves axially with the carriageassembly 25 at precisely the same rate, and continuous rotation of thedrum sequentially presents the character elements 24 thereon to theassociated hammers 28 for printing, as will subsequently be described indetail. When the farthest extent of the carriage assembly 25 and drum 20has been attained (near the right end of the printer) the resetting arm49 is actuated to disengage the pin 31 and permit the spring 40 toreturn the mechanisms to the home position near the left end.

FIG. 2 shows one inking arrangement and best illustrates the individualraised character elements 24 of the printer. The paper 50 is positionedby conventional web positioning means 2 between the drum 20 and thehammers 28 which are aligned on a common axle 52 for pivotal movementtoward the paper 50 and drum 20. The hammers 28 have enlarged heads 54,and foot portions 56 made of magnetic material and angularly offsetrelative to the axle 52 to best accommodate the magnetic coils 58 bywhich the hammers 28 are actuated. An inking roll 60 is rotatablymounted upon a shaft 62 that is parallel to shafts 12 and 52, and theroll 60 moves with the drum 20 and contacts the character elements 24 toprovide ink thereto for transfer upon impact. It will be appreciatedthat this arrangement for inking would not be very appropriate with themechanism shown in FIG. 1 because printing would thereby be producedfrom right to left on the page. With the particular printer illustrated,it is preferable to supply an inking ribbon 55 from spools 57 and conveyit between the hammers 28 and paper 50. The impressions are therebytransferred from the drum through the rear of the paper 50 forreproduction on the front surface thereof.

With further specific reference to FIG. 1, it is seen that each of theenlarged heads or impact members 54 of the hammers 28 is substantiallyequal in width to the axial portion of the drum 20 that is covered bythe character group (e.g. A A A B B or B that is associated with it;i.e., each head 54 is about one-sixth of the total length of the drum20. As a result, each head 54 is capableof contacting all elements 24 ofthe character group with which it is aligned, and only those elements.

Appropriately interconnected (in a manner not shown) with the otherelements of the printer is a schematically represented electronic logicsystem 64, used for information input and printout control. Normally,the electronic system 64 will cooperate with a computer or other centralprinting unit providing data input thereto, and the logic design will bemore fully described hereinafter. m

The timing wheel 18 on the end of the hexagonal shaft 12 is providedwith reference marks or strobes (not shown) indicative of the positionof eachof the character elements 24 on the drum 20. The wheel may alsohave marks for other purposes, such as to enable tabulation of totalrevolutions of the drum for carriage return control and the like, or asecond timing wheel may be provided'for that purpose. The wheel 18passes through the field of a magnetic pickup head 66, which isconnected to the system 64, to generate a signal for actuation of thehammers 28 when the character required in a particular column of thepaper 50 is aligned therewith (as indicated by the signal from head 66).It will be appreciated that other means for detecting the relationshipbetween the character elements 24 and the hammers 28 or heads 54 may besubstituted, such as the optical code diskdevices known in the art. Itwill also be. appreciated that the arrangement of character elements 24illustrated in FIG. 3 simplifies the timing wheel configuration sincelike elements of each character set are aligned and may all therefore beindicated by a single reference mark; however, other characterarrangements may be employed advantageously. The limit switch 68 isactuated by the carriage assembly in the home position thereof, topermit the transfer of data through the electronic system 64 and theother parts of the printer.

As depicted in FIG. 1, the drum 20 rotates upwardly into the page ofdrawings while it moves axially from left to right. To compensate forthe axial movement, it is necessary that the character elements 24 bearranged along a path that extends helically in the direction oppositeto forward progression of the drum 20. This allows all elements of eachcharacter group to pass the same points across the page, and it will beappreciated that the proper helical angleis a function of the axial androtational rates, and of the character group spacing. If movement wasintermittent or at varying rates, the elements would have to be arrangedalong paths of different configurations for proper compensation.

As has been mentioned, the drum 20 employed in FIGS. 1 3 has sixseparate character groups (namely A A A B B and B each of which isassociated with a single hammer 28. Each of the pairs of groups A,

and B A, and B and A and B, constitutes asingle alphanumeric series(normally of 64 or 96 characters) to provide three complete charactersets on the drum 20, the groups A, and B being positioned to sweep everythird column on the page (e.g., columns 2, 5, 8, l1 the groups A, and B,sweeping subsequent columns (e.'g., 1, 4, '7, 10 and A and B sweepingthe remaining columns (e.g., 3, 6, 9, l2. In this manner a fullalphanumeric character set is presented to each column of the page asthe drum 20 progresses thereacross, and the speed of printing can begreatly increased because each of the sets need pass only one third ofthe columns. Moreover, due to the division of each set into two axiallyoffset groups, the speed is further increased by elimination of anydelay due to hammer responsiveness and cycle times. Thus, by so dividingthe character sets the equivalent of l of blank space is provided forthe resetting of each of the hammers between impacts, which is more thanadequate recycle time, in thepresent state of the art. Although it mightappear that even greater printing rates could be attained by dividingthe sets into more than two groups, such is not the case in practice.The resultant speeds require very high rates of drum rotation, which inturn would impose intolerable centrifugal forces thereon. Secondly,although the contact time of the paper, character elements, and impactheads is very brief, unduly high speeds cause significant relativemovement at the moment of contact, producing smudg'ing and loss ofdefinition in the printed characters. in FIG. 5, a developed (i.e.,showing the full 360 circumferential surface) drum 20' having only twocharacter groups C, D is illustrated, the groups C and D constituting asingle alphanumeric series. The carriage 25' supports two hammers-28',each of which has an impact head 54' spanning the axial length of thecharacter group with which it is aligned. Although this embodiment doesnot offer the full scope of benefits previously discussed, the printingspeeds attainable are considerably in excess of those that would bepossible using a drum having the character set arranged along a single,continuous (not offset) helical path and associated with only onehammer. Thus the recycle time for the hammer must be accounted for inthe latter instance, and although the lag is brief it imposes asignificant limitation upon printing speeds. It will be appreciated thatother character configurations than those illustrated may. be employedin accordance with the instant invention, such asconfigurations-providing two or four complete character sets about thedrum circumference.

FIG. 6 illustrates another embodiment of the invention wherein thedeveloped drum 20" has three axially offset character sets E, F and Gthereon, cooperating with a carriage assembly 25" having three hammers28" and associated impact heads 54'. The provision bf a plurality ofcharacter sets in accordance herewith permits increased printingratesbecause only a fraction of the total number of columns must be coveredby each set. However, since only one hammer 28".

cooperates with each set of characters, the cycle time of the hammersmust be considered,.thus rendering this arrangement less desirable thanthat illustrated in FIGS. 1 3 wherein both a plurality of character setsand also offset character groups comprising half a set are employed.Resetting time is accounted for in this embodiment by providingcircumferential spaces h between the first character (A) and the lastcharacter (Z) in each alphanumeric set E, F and G. The worst possiblecase with such an arrangement would require the letter Z to be printedin one column, and immediately thereafter the letter A to be printed inthe next; the space h provides a relief period for hammer resetting,making such an operation possible at the high speeds that are attainabledue to the use of plural character sets.

It should be understood that operation of the printer herein describedrequires that the hammers be capable of independent and arbitrary ornon-sequential actuation, since the character to be printed in aparticular column will be presented thereto without regard to theposition of the column relative to those in the same vicinity. To permitoperation in such a manner, the computer, data terminal,telecommunication system or other central printing unit must be employedwith logic design capable of producing such results. FIG. 7 of thedrawings schematically illustrates an appropriate design for use withthe printer of FIGS. 1 3.

Actuation of the limit switch (68 in FIG. 1) permits initialcommunication to occur between the printer and data supplier or centralprocessing unit (CPU in FIG. 7). Upon every revolution of the drum 20the. print mechanism, through the timing wheel 18 and pickup head 66,signals or flags the CPU of its availability for data input. The CPUthereupon serially transmits data, a character code at a time, to theinput buffer registers A, B and C. Assuming, for example, the matter tobe printed to be the word prints," the p code would go to register A,the r code to register B, and the 1' code to register C (hereafter onlythe letters themselves, rather than their codes, will be referred to).Upon transmission of the third character, the flag signal is removed toterminate data inflow.

A reference mark on the timing wheel 18 (which, along with the shafts l2and 14 and the'drum 20 is con? tinuously rotating) actuates theengagement mechanism of the carriage assembly and causes it and the drum20 to be driven axially thereby. A subsequent mark effects a shift ofthe data in registers A, B and C I to shift registers 10, 11 and 12respectively, placing p in 10, r in 11 and iin 12. At this point, thecharacter elements (a m) in the group designated A begin to sweepthrough the third column location on the page. Rotation of the timingwheel 18 generates pulses which are counted and stored in a six bitcounter (CTR.) to indicate the presence of each character element as itbecomes available for printing in column 3. During the first half 180)of the drum revolution the content of the CTR is compared with that ofshift register 12 in the first comparator (COMP. 1). Since, in fact thecharacter i is present in both register 1 and the counter(representative of an A character group), a signal is generated toactivate solenoid A, and its associated hammer 28 to print the characterin column 3 of the page. During the second half of the first revolutionof the drum the character group B (containing elements n z) sweeps thesecond column location and BUS 1 switches the comparison in COMP. 1 tothe CTR content and that of shift register 11. Since,once again, boththe register compared and the counter (now representative of a Bcharacter group) contain a common character (i.e., r) solenoid B, isactivated to print with the proper hammer 28 in column 2. Thus, afterthe first complete revolution the page bears the characters ri.

While this was happening, the previously mentioned flag is set and threemore characters are stored in the buffer registers; i.e., n is stored inA, t is stored in B and s is stored in C, after which the flow of datais terminated. A reference strobe generated between the first and secondrevolutions shifts any remaining data in registers 10, 11 and 12 toregisters 7, 8 and 9 respectively, and the data in the buffer registersto shift registers 10, 11 and 12 in the manner previously described. Asa result, during the second revolution of the drum characters p, n, tand s are inregisters 7, 10, 11 and 12 respectively, registers 8 and 9being vacant since the characters r and i were printed during the firstrevolution. During the first half of the second revolution charactergroups A; and A, sweep columns 6 and 1 respectively, the counteraccumulates characters a m and comparators 1 and 2 compare the contentsof shift registers 12 and 7 respectively. Since these registers containonly B group characters (i.e. in the latter half of the alphabet) nomatch is found and no printing occurs. However, during the second halfrevolution, while character group B sweeps column 5, the counteraccumulates the B group characters and comparator l finds the charactert in register 11; accordingly, solenoid B activates its associatedhammer 28 and prints the character t in column 5.

1 At the beginning of the third revolution the data has been shifted sothat p, n and s are in registers 4, 7 and 9, registers 10, 11 and 12being vacant because the matter to be printed has been fullytransmitted. During this revolution comparisons are made as hereinbeforedescribed while groups A B A, and B sweep columns 9, 8, 4 and 3,respectively; no matches are found, and no printing therefore occurs. Onthe fourth revolution the data is shifted to place p in register 1 and nand s in registers 4 and 6. During the second half revolution, whilegroups 8;, and B, sweep columns 6 and 1 respectively, matches are foundby both comparators 2 and 3. As a result, the characters p and s areprinted in columns 1 and 6, and the page contains the characters prits.Thereafter, the character n shifts to register 1 and, while group B,passes column 4 a match causes the final character to be printed tocomplete the word.

The logic system will vary depending upon the number of charactergroups, the arrangement thereof and other factors to provide the properfiring order. Normally it will also include circuitry for carriagereturn, which may continuously monitor register A to detect the code forcarriage return, which in turn may be generated by the counter aftersensing an appropriate number of drum revolutions. Upon detecting such acode, a signal is generated to activate the release arm 49, to disengagethe pin 31 from the shaft 14 and permit the spring 40 to return thecarriage 25. In addition, another detector may detect a line feed codeat the input, and fire a paper advance solenoid (not shown) to permitprinting of a subsequent line. Such circuitry should be appropriatelydesigned to prevent data flow when undesired, such as during carriagereturn, or to permit over-printing by delaying paper advance.

Although it is believed that the foregoing detailed description willenable those skilled in the art to readily practice the invention,perhaps it should be noted that the optimum overall dimensions for thetype of character drum illustrated in FIGS. 1 3 are believed to be about2.6 inches in diameter and 1.5 inches in width (axial length). Thesedimensions are thought to result in a weight/mass to volume ratio thatis particularly desirable in a rotating drum of such configuration for anumber of reasons, including the elimination of the need for anextensive and costly bearing set for absorption of hammer impact shockduring printing. The drum impact surfaces are preferably plated with ahard metal such as chromium to enhance durability. However, anoutstanding benefit attendant to the unique design features of thepresent printer, which minimize rotational speeds, g loadings andtorques, is the potential for use of non-ferrous materials, which canoften conveniently and inexpensively be molded.

Thus, it can be seen that the present invention attains the primaryobject thereof, namely the provision of a novel medium speed electronicprinter that is relatively inexpensive to produce. Furthermore, theprinter is capable of printing at least 30 characters per second, and ofprinting at the preferred and most desirable rates of 60 90 and 80 120characters per second, respectively, thus overcoming limited throughputcapability of prior art output devices and providing a printer that isespecially suited for use in mini-computer systems. The inventionprovides a full character impact printer having, in addition to theforegoing advantages, the capability of producing a desirable final copyformat, as well as providing a novel method of electronically printingat a medium rate, as is also an object of the invention.

Having thus described the invention, I claim:

1. In an electronic character printer, the combination comprising:

a. a frame having means thereon for positioning a web to be printedalong a linear printing path;

. a character drum mounted on said frame for concurrent movement alongsaid linear path and rotation about an axis parallel thereto, said drumhaving a multiplicity of character elements arranged about thecircumference thereof and along helical paths, said elements beingdivided into a plurality of discrete, axially ofiset character sets eachcomprised of a plurality of discrete, axially offset character groupseach provided by a multiplicity of character elements, each of saidcharacter sets extending about substantially the entire circumference ofsaid drum;

. a multiplicity of impact members mounted on said frame for synchronousmovement along said linear path with said character drum and equal innumber to the total number of character groups cooperating therewith,each of said impact members being of a width substantially equal to theaxial length encompassed by one of said character groups and beingaligned therewith to permit contact to be effected between any characterelement thereof and the web, for printing during said concurrentmovement and rotation;

(1. means for continuously rotating said character drum;

e. means for moving said character drum and impact members along saidlinear path;

f. means for dynamically indicating the angular relationship of thecharacter elements of each of said groups and said impact memberassociated therewith; and

g. means responsive to an electronic input signal representative ofmatter to be printed for actuating said impact members when a desiredcharacter for printing is aligned therewith, as indicated by saidindicating means, said actuating means actuating said impact membersindependently of one another with the impact members cooperating withgroups axially aligned along the length of said drum being actuatedprior to actuation of impact members cooperating with groups spacedcircum ferentially therefrom.

2. The printer of claim 1 wherein said groups are substantiallyidentical in the number and identity of characters; wherein the rates ofrotation and linear movement are predetermined relative to the angle ofsaid helical paths and the character group offset distance to cause thecharacter elements of each of said groups to sweep past only l/n of thenumber of columns to beprinted on the web, where n represents the numberof character sets; and wherein each of said groups extends incompletelyabout said drum circumference to provide circumferential spacing betweenthe first and last character elements thereof.

3. The printer of claim 1 wherein a pair of said groups provides'asingle character set, said set thereby having two of said impact membersassociated therewith.

4. The printer of claim 3 wherein said character groups are arrangedsequentially about the circumference of said drum, with the rates ofrotation and linear movement being predetermined relative to the angleof said helical paths and the character group offset distance to causethe character elements of each ofsaid sets to sweep past only 1/11 ofthe total number of columns to be printed on the object, where nrepresents the number of character sets.

5. The printer of claim 4 wherein there are three of said character setsand six of said impact members.

6. The printer of claim 5 wherein the last character element of one ofsaid groups and the first character element of another of said groups ofits set and to which it is adjacent are axially offset but contiguous toavoid substantial spacing therebetween, and each of said groups occupiesof drum circumferential surface.

7. The printer of claim 3 wherein said character set contains 64alphanumeric characters.

8. The printer of claim 1 additionally including means furnishing ink tothe object at the locations of contact with said character elements.

9. In a printing method, the steps comprising:

a. positioning a web to be printed along a linear printing path;

b. providing a character drum having a multiplicity of characterelements arranged about the circumference thereof and along helicalpaths, said elements being divided into a plurality of discrete, axiallyoffset character sets each comprised of a plurality of discrete, axiallyoffset character groups each provided by a multiplicity of characterelements, each of said character sets extending about substantially theentire circumference of said drum;

c. concurrently moving said character drum along said linear path whilecontinuously rotating said drum about an axis parallel thereto,

d. moving a multiplicity of impact members synchronously with said drumalong said linear path and with said object therebetween, each of saidimpact members cooperating with one of said groups and being of a widthsubstantially equal to the axial length encompassed by one of saidcharacter groups and aligned therewith to permit contact to be effectedbetween any character element thereof and said web;

. dynamically detecting the relationship between the character elementsof each of said groups and said impact member associated therewith andgenerating an electronic signal representative thereof;

f. generating an electronic input signal representative of matter to beprinted;

g. comparing said detecting signal and said input signal; and

h. independently actuating said impact members in response. to saidsignal comparison during said concurrent movement and rotation to effectcontact of said web with said character elements to reproduce saidmatter on said web, said actuation during a single rotation of said drumbeing of the impact members cooperating with character groups axiallyaligned along the length of said drum prior to actuation of impactmembers cooperating with groups spaced circumferentially therefrom.

10. The method of claim 9 wherein said impact members are actuated at arate to contact 60-90 of said character elements per second with saidweb.

11. The method of claim 9 wherein said impact members are actuated at arate to contact -120 of said character elements per second with saidweb.

1. In an electronic character printer, the combination comprising: a. aframe having means thereon for positioning a web to be printed along alinear printing path; b. a character drum mounted on said frame forconcurrent movement along said linear path and rotation about an axisparallel thereto, said drum having a multiplicity of character elementsarranged about the circumference thereof and along helical paths, saidelements being divided into a plurality of discrete, axially offsetcharacter sets each comprised of a plurality of discrete, axially offsetcharacter groups each provided by a multiplicity of character elements,each of said character sets extending about substantially the entirecircumference of said drum; c. a multiplicity of impact members mountedon said frame for synchronous movement along said linear path with saidcharacter drum and equal in number to the total number of charactergroups cooperating therewith, each of said impact members being of awidth substantially equal to the axial length encompassed by one of saidcharacter groups and being aligned therewith to permit contact to beeffected between any character element thereof and the web, for printingduring said concurrent movement and rotation; d. means for continuouslyrotating said character drum; e. means for moving said character drumand impact members along said linear path; f. means for dynamicallyindicating the angular relationship of the character elements of each ofsaid groups and said impact member associated therewith; and g. meansresponsive to an electronic input signal representative of matter to beprinted for actuating said impact members when a desired character forprinting is aligned therewith, as indicated by said indicating means,said actuating means actuating said impact members independently of oneanother with the impact members cooperating with groups axially alignedalong the length of said drum being actuated prior to actuation ofimpact members cooperating with groups spaced circumferentiallytherefrom.
 2. The printer of claim 1 wherein said groups aresubstantially identical in the number and identity of characters;wherein the rates of rotation and linear movement are predeterminedrelative to the angle of said helical paths and the character groupoffset distance to cause the character elements of each of said groupsto sweep past only 1/n of the number of columns to be printed on theweb, where n represents the number of character sets; and wherein eachof said groups extends incompletely about said drum circumference toprovide circumferential spacing between the first and last characterelements thereof.
 3. The printer of claim 1 wherein a pair of saidgroups provides a single character set, said set thereby having two ofsaid impact members associated therewith.
 4. The printer of claim 3wherein said character groups are arranged sequentially about thecircumference of said drum, with the rates of rotation and linearmovement being predetermined relative to the angle of said helical pathsand the character group offset distance to cause the character elementsof each of said sets to sweep past only 1/n of the total number ofcolumns to be printed on the object, where n represents the number ofcharacter sets.
 5. The printer of claim 4 wherein there are three ofsaid character sets and six of said impact members.
 6. The printer ofclaim 5 wherein the last character element of one of said groups and thefirst character element of another of said groups of its set and towhich it is adjacent are axially offset but contiguous to avoidsubstantial spacing therebetween, and each of said groups occupies 180*of drum circumferential surface.
 7. The printer of claim 3 wherein saidcharacter set contains 64 alphanumeric characters.
 8. The printer ofclaim 1 additionally including means furnishing ink to the object at thelocations of contact with said character elements.
 9. In a printingmethod, the steps comprising: a. positioning a web to be printed along alinear printing path; b. providing a character drum having amultiplicity of character elements arranged about the circumferencethereof and along helical paths, said elements being divided into aplurality of discrete, axially offset character sets each comprised of aplurality of discrete, axially offset character groups each provided bya multiplicity of character elements, each of said character setsextending about substantially the entire circumference of said drum; c.concurrently moving said character drum along said linear path whilecontinuously rotating said drum about an axis parallel thereto, d.moving a multiplicity of impact members synchronously with said drumalong said linear path and with said object therebetween, each of saidimpact members cooperating with one of said groups and being of a widthsubstantially equal to the axial length encompassed by one of saidcharacter groups and aligned therewith to permit contact to be effectedbetween any character element thereof and said web; e. dynamicallydetecting the relationship between the character elements of each ofsaid groups and said impact member aSsociated therewith and generatingan electronic signal representative thereof; f. generating an electronicinput signal representative of matter to be printed; g. comparing saiddetecting signal and said input signal; and h. independently actuatingsaid impact members in response to said signal comparison during saidconcurrent movement and rotation to effect contact of said web with saidcharacter elements to reproduce said matter on said web, said actuationduring a single rotation of said drum being of the impact memberscooperating with character groups axially aligned along the length ofsaid drum prior to actuation of impact members cooperating with groupsspaced circumferentially therefrom.
 10. The method of claim 9 whereinsaid impact members are actuated at a rate to contact 60-90 of saidcharacter elements per second with said web.
 11. The method of claim 9wherein said impact members are actuated at a rate to contact 80-120 ofsaid character elements per second with said web.